In response to concerns that volcanic ash ejected during the 2010 eruptions of Eyjafjallajökull in Iceland would damage aircraft engines, the controlled airspace of many European countries was closed to instrument flight rules traffic, resulting in what at the time was the largest air-traffic shut-down since World War II. The closures caused millions of passengers to be stranded not only in Europe, but across the world. With large parts of European airspace closed to air traffic, many more countries were affected as flights to, from, and over Europe were cancelled.
An eruption on 14 April led to an initial uninterrupted shutdown over much of northern Europe from 15 to 23 April. Afterwards, airspace was closed intermittently in different parts of Europe in the following weeks, as the path of the ash cloud was tracked. The ash cloud caused further disruptions to air travel operations in Scotland and Ireland on 4 and 5 May and in Spain, Portugal, northern Italy, Austria, and southern Germany on 9 May. Irish and UK airspace closed again on 16 May and reopened on 17 May.
The eruption occurred beneath glacial ice. The cold water from the melting ice chilled the lava quickly, causing it to fragment into very small particles of glass (silica) and ash, which were carried into the eruption plume. The extremely fine ash particles and the large volume of steam from the glacial meltwater sent an ash plume hazardous to aircraft rapidly high into the upper atmosphere. The presence and location of the plume depended upon the state of the eruption and the winds. The large amount of glacial meltwater flowing into the eruption vent made this eruption so explosive that it ejected its ash plume directly into the jet stream, which was unusually stable and south-easterly. The ash was then carried over Europe into some of the busiest airspace in the world.
The International Air Transport Association (IATA) estimated that the airline industry worldwide would lose (, ) a day during the disruption. IATA stated that the total loss for the airline industry was around €1.3 billion (£1.1 billion, US$1.7 billion). The Airport Operators Association (AOA) estimated that airports lost £80 million over the six and a half days. Over 95,000 flights had been cancelled all across Europe during the six-day airspace ban, with later figures suggesting 107,000 flights cancelled during an 8-day period, accounting for 48% of total air traffic and roughly 10 million passengers.
Background
The London Volcanic Ash Advisory Centre (VAAC) was responsible for providing information about the ash plume to the relevant civil aviation authorities in the form of Volcanic Ash Advisories (VAA). On the basis of this, the authorities made decisions about when and where airspace should be closed due to the safety issues. Their decisions resulted in the cancellations of flights at airports across the world, not only in those countries where airspace was restricted. On 16 April 2010, 16,000 of Europe's usual 28,000 daily scheduled passenger flights were cancelled and on the following day 16,000 of the usual 22,000 flights were cancelled. By 21 April 95,000 flights had been cancelled."Ash cloud chaos: Airlines face huge task as ban ends" BBC News, 21 April 2010
Before this, the most severe restrictions to air travel in recent times were following the attacks of 11 September 2001 in the United States when all civil air traffic (not just scheduled) in US airspace, and to and from the United States, was grounded for three days.
Professor Bill McGuire of the Aon Benfield UCL Hazard Research Centre said on 15 April that the most notable eruption of the Icelandic volcano Laki (which occurred in 1783,"Icelandic Volcano Caused Historic Famine In Egypt, Study Shows " ScienceDaily 22 November 2006), if it occurred today, would "have the potential to severely affect air travel at high northern latitudes for six months or more". The last time the Eyjafjallajökull volcano erupted, in 1821, it spewed ash for over a year."Volcano could mean cooling, acid rain " NBC News, 15 April 2010 Geophysicists in Iceland said that the production of ash from Eyjafjallajökull was likely to continue at a comparable level for some days or even weeks; a geophysicist at the Icelandic Meteorological Office said, "Where it disrupts travel depends on the weather. It depends how the wind carries the ash"."Volcano chaos as Iceland eruption empties skies in Britain" The Guardian newspaper, 16 April 2010
Jet engine tolerance to airborne particles
In 1982, British Airways Flight 9 flew through volcanic ash of Mount Galunggung, Java, Indonesia, causing all 4 engines to shut down. However, the crew restarted all but one of the engines and landed safely. Subsequently, there was an addition to the operations manuals, describing how to deal with volcanic ash.
In 1989, KLM Flight 867 was on its approach into Anchorage, Alaska when the Boeing 747-400 flew through volcanic ash from Mount Redoubt causing all 4 engines to shut down. The crew were able to restart both engines on the left wing and landed safely in Ted Stevens International Airport.
Iceland's authorities had been warning airlines for several years, asking them to determine the density of ash that is safe for their jet engines. However, prior to the volcanic events of April 2010, aircraft engine manufacturers still had not defined specific particle levels above which engines were considered to be at risk. The general approach taken by airspace regulators was that if the ash concentration rose above zero, then the airspace was considered unsafe and was consequently closed.
The April eruption of Eyjafjallajökull caused enough economic difficulties that aircraft manufacturers were forced to define specific limits on how much ash is considered acceptable for a jet engine to ingest without damage. On 21 April, the UK's Civil Aviation Authority (CAA) in conjunction with engine manufacturers, set new guidelines which allowed aircraft to fly when there are levels of volcanic ash between 200 and 2000 micrograms (2 milligrams) of ash per cubic metre. These levels were declared by governments, aircraft manufacturers, and airlines not to have safety implications if appropriate maintenance and ash inspection procedures were followed.Was the flight ban necessary? BBC News, 21 April 2010Volcano ash flight ban 'might have ended sooner' BBC News, 3 May 2010
From noon 18 May, the UK CAA further revised the safe limit upwards to 4 milligrams per cubic metre of air space. Any airspace in which the ash density exceeds this limit is categorised as prohibited airspace.
To minimise the level of further disruption that this and other volcanic eruptions could cause, the UK CAA announced the creation of a new category of restricted airspace called a Time Limited Zone (TLZ). Airspace categorised as TLZ is similar to airspace experiencing severe weather in that the restrictions are expected to be of a short duration; however, the key difference with TLZ airspace is that airlines must produce certificates of compliance in order for their aircraft to enter these areas. Flybe was the first airline to conform to these regulations and their aircraft will be permitted to enter airspace in which the ash density is between 2 mg and 4 mg per cubic metre.
Airspace restrictions in Europe
Under international regulations, all scheduled passenger flights operate under the instrument flight rules (IFR) which requires clearance to be obtained from air traffic control. From 14 April onwards, the controlled airspace was closed in several European countries and no IFR clearances were granted. The airspace of Iceland itself was hardly disrupted in this period (although a change in the wind direction on 23 April caused the main airport to be closed).
By 23 April, the restrictions were lifted over much of Europe through the introduction of new guidelines on volcanic ash density. After this date there were sporadic closures from time to time, notably in the UK, Ireland, and Iceland, but not a blanket shutdown.
Country Restrictions imposed On 16 April, Austro Control ceased air activities at airports in both Vienna and Linz; Salzburg and Innsbruck stopped flights at 20:00 CEST; and Graz and Klagenfurt followed at 23:00 CEST. At 00:30 on 18 April, all Austrian airports were closed until 18:00.Austria starts closing airspace due to volcano ash Business Week, 16 April 2010 The Austria Press Agency reported that permission to resume takeoffs and landings took effect at 05:00 local time (0300 UTC) Monday but that it was unclear whether the airspace would remain open all day.Germany lets Lufthansa fly 15,000 back home ajc.com, 19 April 2010 On Saturday 17 April, the airspace over Belarus was closed. Belgium's airspace closed at 16:30 CEST on 15 April. It remained closed until 08:00 CEST on Tuesday 20 April.Morgen gedeeltelijke hervatting vliegverkeer De Redactie, 19 April 2010 The airspace over Bosnia and Herzegovina was closed to traffic from 08:00 CEST until midnight (00:00 CEST) on 17 April.Bosnia closes airspace to 2200 GMT: official Agence France-Presse – MSN News, 17 April 2010 On Sunday 18 April, all Bulgarian airports were closed. However, at 14:00 local time the airports in Sofia and Plovdiv were open. At 02:00 CET on 17 April, the air space over northern Croatia was closed, including Zagreb. At 08:00 CET the airports at Pula, Rijeka, Zadar, and Lošinj were closed. Naviair, the state-owned company controlling Danish airspace, announced that Denmark's airspace would close at 16:00 UTC on 15 April. However, Naviair assessed that it is safe to fly through airspace in high altitude – .